While it is clear that astrocytes exhibit properties that could enable them to modulate neuronal activity in vivo, we believe that it is essential to develop model systems whereby the role of astrocytes in neurophysiology and behavior can be examined. To accomplish this goal, we have developed conditional gene knockout systems that enable us to examine the role of specific astrocytic gene products in developing and mature mice. We plan to use astrocyte-specific, inducible knockout (i-cKO) mice to test the hypothesis that during neuronal activity, astrocytes take up K+ through Kir4.1 channels and disperse this ion through an astrocytic syncytium created by connexin43-based gap junctions. We have prepared an inducible Cre-loxP system that enables us to inactivate "floxed" genes in greater than 95% of astrocytes during development and post-developmentally. Experiments using hippocampal brain slices will be carried out to determine if an astrocyte-specific, i-cKO of Kir4.1 or Cx43 affects K+ homeostasis, and/or neuronal excitability in situ, and animal behavior. We have also prepared non-inducible Kir4.1 and Cx43 cKO mice that exhibit striking cellular and behavioral changes. Non-inducible Kir4.1 cKO mice exhibit aberrant myelination throughout the brain and spinal cord. We will test the hypothesis that the abnormal myelination observed in non-inducible Kir4.1 cKO mice arises from a defect in either the development of oligodendrocytes or the ability of mature oligodendrocytes to maintain myelin. Over the past several years we have developed a number of molecular tools that enable us to carry out astrocyte-specific inducible gene knockouts. These molecular tools, combined with floxed mice being generated in this and other laboratories, will be extremely useful in studying the function of astrocytes in processes ranging from synaptic plasticity at the cellular level to learning and memory at the behavioral level. We propose to develop a website describing the genetic models developed in our laboratory to enable others to take full advantage of these reagents in unraveling the role of astrocytes in neurophysiology and behavior. [unreadable] [unreadable]